The principal objectives of this proposal are to map and to characterize the inheritance of the H-2-linked genes which influence susceptibility and resistance to infection with Trichinella spiralis in the mouse, to determine the developmental stages in the parasite's life history which are influenced by the genes identified, and to begin characterization of the specific cell types mediating immunity to this parasite. These objectives will be addressed by studying infections in congenic strains of mice which differ only at genes within the H-2 complex but demonstrate different levels of resistance to infection with T. spiralis. Alloantisera specific for the products of H-2-linked genes and for the Ly antigens expressed on the surface of functionally defined subpopulations of lymphoid cells, will be used to selectively deplete certain cell types from populations of cells isolated for study. These antiserum-treated cell populations, lacking specific subsets of immunoreactive cells, will then be tested to see if their in vitro proliferative response to Trichinella antigen has been altered or if they differ in their ability to adoptively transfer resistance to previously uninfected, syngeneic hosts. Altered activity following antiserum treatment will implicate cells bearing the appropriate specificity as important in contributing to the response being investigated.